I think the boost gets it up to pressure with the 150, speed ought to be about the same as a caseful of 4350, 2600-2700fps.  Someday, I'll get a chronograph.  The boost seems to get the 860 powder burning about the same speed as the old H450.  I started at 3.5gr with the booster and I've worked up in approx .2gr increments.  I'll have to prove my guesses at some point.